Such a hearing protector is known from DE-A-40 08 982, which discloses a substantially solid sealing body which is made to measure for a particular user (otoplastic). The sealing body contains an aeration channel which is widened at the proximal end part. A muffling device is fitted in the widened end part. The muffling device consists of a cylindrical element which is provided with a through aperture. The through aperture is made eccentrically in the element, the diameter of the aperture corresponding approximately to the diameter of the aeration channel. On the front side, the element is provided with a slot in which a screwdriver can engage. In this way, the element can be rotated relative to the sealing device, with the result that the aeration channel is cleared to a greater or lesser extent by the through aperture.
A disadvantage with this known hearing protector is that the muffling device is difficult to control. If a specific muffling value is desired, said value is difficult or impossible to set or distinguish. The design of the muffling element is intended in particular for otoplastics, and it is ill suited for use on a hearing protector with a sealing body of a more open design intended for universal use. In the open position of the muffling device, inadequate sound muffling can be achieved as a result of the relatively large diameter of the through aperture in the cylindrical element. In the fully closed position of the muffling device, undesired acoustic leakage still occurs. Moreover, the muffling device cannot be controlled without an aid.
EP-A-0 333 298 and DE-U-93 13 061 disclose hearing protectors with muffling devices, in which the muffling device comprises a housing which is fixed in the channel of the sealing body and comprises a central bore, consisting of a cylindrical threaded part and a part which tapers in the distal direction. A correspondingly threaded adjusting pin, which is formed such that it is complementary to the tapering part of the bore, fits into the bore, which pin can be moved in the axial direction by rotation in the bore, with the result that the passage to the open environment can be adjusted. This permits a stepless adjustment of the passage, and thus of the muffling action of the muffling device. Said stepless adjustment of the muffling action is used for having the muffling action set once by a manufacturer, by way of measurement, at a value specified by a user.
As in the case of DE-A-40 08 982, it is also a disadvantage in this type of hearing protector that the muffling device is difficult to control. Any change in the muffling value to a different muffling value will usually have to be carried out again by the manufacturer by means of rotating the adjusting pin and at the same time measuring the muffling value. The setting of the muffling value will generally not be changed by the user. However, if the user still changes the setting of the muffling device himself, it will have to be carried out by feel, and there is a risk here that a muffling effect which is correct by feel will turn out to be too low a muffling value in certain circumstances, so that the user, without noticing it, runs the risk of hearing loss in the long run.